1. Field
The disclosed concept relates generally to electrical switching apparatus and, more particularly, to electrical switching apparatus, such as circuit breakers. The disclosed concept also relates to trip latch assemblies for electrical switching apparatus.
2. Background Information
Electrical switching apparatus, such as circuit breakers, provide protection for electrical systems from electrical fault conditions such as, for example, current overloads, short circuits, abnormal voltage and other fault conditions. Typically, circuit breakers include an operating mechanism, which opens electrical contact assemblies to interrupt the flow of current through the conductors of an electrical system in response to such fault conditions as detected, for example, by a trip unit. The electrical contact assemblies include stationary electrical contacts and corresponding movable electrical contacts that are separable from the stationary electrical contacts.
Among other components, the operating mechanisms of some low and medium voltage circuit breakers, for example, typically include a pole shaft, a trip actuator assembly, a closing assembly and an opening assembly. The trip actuator assembly responds to the trip unit and actuates the operating mechanism. The closing assembly and the opening assembly may have some common elements, which are structured to move the movable electrical contacts between a first, open position, wherein the movable and stationary electrical contacts are separated, and a second, closed position, wherein the movable and stationary electrical contacts are electrically connected. Specifically, the movable electrical contacts are coupled to the pole shaft. Elements of both the closing assembly and the opening assembly, which are also pivotably coupled to the pole shaft, pivot the pole shaft in order to effectuate the closing and opening of the electrical contacts.
For example, typically when the circuit breaker is open, a trip latch spring applies torque to a trip latch to reset the circuit breaker and prepare it for closing. If, however, the circuit breaker does not reset, for example because of relatively weak spring force, the circuit breaker will attempt to close but be unable to because the trip latch is not reset. This can result in damage to circuit breaker components. Furthermore, the problem is exacerbated by the desire to use as few springs as possible with the smallest spring force possible for resetting in an attempt to avoid an undesirable balance of springs, wherein some springs (e.g., without limitation, opening springs) are trying to open the breaker and some springs (e.g., without limitation, closing springs) are trying to close the breaker.
There is, therefore, room for improvement in electrical switching apparatus, such as circuit breakers, and in trip latch assemblies therefor.